Generally, a vehicle seat device is provided with a seat lifter device for adjusting the height of the seat cushion and the seat lifter device is operated by operating an operating lever under a condition that an occupant of the seat is seated on the seat cushion to adjust the height of the seat cushion. One of such vehicle seat lifter devices is disclosed in a Patent Document 1.
The vehicle seat lifter device described in the Patent Document 1 uses a roller clutch mechanism for changing over the motion of the operating lever and frictionally keeping the lifted position of the seat by rollers and the seat lifter device uses a parallel link mechanism having two link members which are rotatably connected by a sector gear and a pinion gear. The pinion gear is rotatably driven by the roller clutch mechanism. An occupant of the seat reciprocates the operating lever from the neutral position to upper or lower position under the occupant being kept seated on the seat. Thus the vehicle seat can be successively raised or successively lowered.